One of Gichin Funakoshi's "forgotten" throws, called by the master in two different ways: 捻倒 / Neji-daoshi ("Twisting downward") in his 1925 book and 獨樂投 / Koma nage ("Spinning top throw") in his 1935 book. Funakoshi Sensei tells us that this throw is an application of the Tekki Shodan kata (ナイハンチ初段の變手 / Naihanchi Shodan no hente).
It is a simple joint lock, here are the key points: use hikite to twist the arm and do not assume that the opponent will let you have his arm outstretched, rather push his body away and the arm will naturally tense up.